#define _CRT_SECURE_NO_WARNINGS 1
#include <cmath>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include<math.h>
#include<stdlib.h>
#include<stdio.h>
#include<unordered_map>
#include<queue>
using namespace std;

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_map<int, int> hash;
        for (auto& num : nums)
        {
            if (hash.count(num)) return true;
            else hash[num]++;
        }
        return false;
    }
};

int main() {
    return 0;
}